Correlation of circulating matrix metalloproteinase-9 (MMP-9) concentrations with skin fibrosis and with concentrations of transforming growth factor β (TGFβ). (a) Correlation of MMP-9 concentrations with skin scores. The extent of skin involvement of systemic sclerosis was determined by modified Rodnan scores. Broken line indicates cutoff value for patients with severe skin involvement (Rodnan score ≥20). Bars represent the mean ± standard error of the mean of MMP-9 in patients with severe versus mild-to-moderate skin involvement (Rodnan score <20). (b) Correlation of circulatory MMP-9 concentrations with TGFβ concentrations.